Telecommunication, data communication, high-performance computing, and the like systems are typically deployed in physical hardware shelves that are rack mounted in racks or frames. For example, typical racks or frames are either 19 or 23 inches in practice. A rack unit (abbreviated as U or RU) is a unit of measure describing the height of equipment intended for mounting in a rack or frame. For example, 1U piece of equipment would take up one rack unit of space in height; a 2U would take up two rack units of space in height, etc. As technology improves and network/computing power increases, the drive is towards smaller and smaller deployments with more functionality and performance. For example, one type of rack configuration is known as a “pizza box” form factor. This is a common design for computers, networking devices, etc. This rack configuration is typically wide and flat, such as 1U or 2U high, thus resembling pizza boxes. Of note, the pizza box form factor is typically an integrated device without modularity. Further, the pizza box form factor or other small RU configurations are constrained by size and cooling constraints. That is, as density increases along with functionality, smaller-sized hardware experiences significant heating issues. There exists a need to accommodate higher-density, smaller-sized hardware via unique cooling mechanisms.
Referring to FIG. 1, in a conventional embodiment, a schematic diagram illustrates a conventional rack unit 10. The conventional rack unit 10 can be a 1U or 2U rack unit, a pizza box form factor, etc. The conventional rack unit 10 generally includes six sides including a top side 12, a bottom side 14, a front side 16, a back side 18, a left side 20, and a right side 22. In a rack-mounted configuration, the left and right sides 20, 22 can be attached in some manner to a rack. The conventional rack unit 10 includes a backplane 24 that is located at or near the back side 18. In this manner, electronics, optics, and other circuitry, hardware, logic, etc. is located within the conventional rack unit 10 and physically connected to the backplane 24. The backplane 24 is parallel to the front and back sides 16, 18. Disadvantageously, air flow through the conventional rack unit 10 is limited due to the vertical backplane 24 which blocks air flow through the conventional rack unit 100. Thus, as the density increases, air flow becomes problematic as the backplane 24 inhibits air flow through the conventional rack unit 10. Accordingly, density suffers and it is difficult to add more functionality in the conventional rack unit 10. Of note, similar problems occur in conventional systems with vertical midplanes instead of the backplane 24. As described herein, the backplane 24, midplanes, etc. are all generally interslot interconnects, and other types of interslot interconnects are also contemplated in addition to the backplane 24, midplanes, etc.
Additional constraints in conventional systems include:
1) Additional density of ports on faceplates on the front side 16 leads to either greater quantity of traces on the backplane 24 and greater quantity of pins on the connectors soldered to the backplane 24, hence bloating the size of the backplane 24 due to routing of traces or of larger connectors;
2) With respect to drastically increasing the quantity of layers in the backplane's 24 printed circuit board (PCB), this is difficult because cost increases super-linearly faster than the increase in quantity of layers;
3) With respect to drastically increasing the bandwidth of each trace in the backplane 24 and pin in each backplane-connector, this is difficult because cost may be prohibitive and/or beyond the current state of the art of Gb/s per bidirectional serializer-deserializer (SerDes) lane; and
4) With respect to drastically shrinking the size of the connectors on the backplane 24, this is difficult because the already rather high Gb/s per bidirectional SerDes lane needs some form of dielectric to eliminate crosstalk and other negative analog effects. If anything, the next generation of higher-bandwidth (-per-pin) connectors are becoming less-dense, not more-dense, to accommodate this additional dielectric material, whether it be plastic or air or other substance. Hence, the challenges tend to worsen over time, not improve.